A cover lens is located at the outermost layer of a touch panel and is a first interface direct linking to a user, closest to the user's finger. The cover lens takes a glass substrate as its substrate material and is adhered to a touch sensor or touch sensor film so as to form a touch panel. However, the existing glass cover lens is relatively heavy and has insufficient impact resistance, and therefore the focus of the market has started to shift to using a plastic substrate to manufacture the cover lens.
Because of low density of the plastic substrate, it can meet user requirements of a thin, light, and portable device (e.g., a smart phone and a tablet). Further, the plastic cover is easily to be shaped to form a curved cover lens due to its perfect processability, and therefore it is easily to apply that to a curved display screen.
FIG. 1 is a schematic diagram showing an existing touch panel manufacture method. The existing touch panel manufacture method is generally to adhere a touch sensor layer 2 connected to a flexible printed circuit board 1 directly to a molded plastic cover 3 so as to manufacture a touch panel 4. Common adhering approaches are edge lamination and full lamination. The edge lamination uses a double faced adhesive to adhere the touch sensor layer 2 to the plastic cover 3 at four edges. The full lamination is to coat an optically clear adhesive (OCA) or an optically clear resin (OCR) between the touch sensor layer 2 and the plastic cover 3, and then they are adhered together. In the full lamination, two plates are fully adhered together without seam or air gap, and therefore light refracting is less likely to occur to affect the display quality. Therefore, compared to the edge lamination, the full lamination becomes a main stream now in manufacturing the touch panel.
However, the touch sensor layer 2 is flat and the plastic cover 3 is curved in the curved cover lens applications. No matter using the edge lamination or the full lamination, there exists a problem of difficulty to adhere the touch sensor layer 2 and the plastic cover 3 and it is hard to avoid the seam and air gap during the manufacture processes.